Siberian peashrub (Caragana arborescens)

Berries and leaves of Amur cork tree

 
 

Siberian peashrub (also known as caragana) is a shrub or small tree that can grow up to 18 feet tall. It has yellow flowers in the tubular shape characteristic of plants in the pea family and produces abundant seedpods. It can compete with native shrubs in forest and savanna environments and overtake grassland areas and convert them to shrublands.

Description

Appearance

Siberian peashrub is an upright shrub or small tree that grows up to 18 feet tall. It has a narrow branching structure. Mature bark and branches are gray while young twigs are yellowish-green.

Leaves and Stem

Leaves are alternate (come off the stem one at time at each leaf node). Leaves are compound and are generally made up of 8-12 elliptic leaflets. The leaflets are in pairs opposite one another. There is no leaflet at the tip of the leaf. Each leaflet can be up to one inch long and the full leaf is 3-5 inches long. Leaflets have smooth edges and a small point at the tip. At the base of the leaves are pairs of stipules which in Siberian peashrub are small, sharp growths that can look like small thorns.

Flowers

Flowers are yellow, single, and tubular in the characteristic shape of plants in the pea family. Flowers grow at the end of a stalk from where the leaf meets the branch. Flowers bloom in May and June.

Seeds

Fruit are 1-2 inch smooth pods that are sharply pointed. New pods are greenish-yellow but become brownish-red as they mature. Each pod contains about six seeds.

Roots

Siberian peashrub has a dense root system. Like other members of the legume (pea) family, the roots have root growths or nodules that house bacteria that can convert nitrogen in the atmosphere into a form of nitrogen that plants can use.

Biology

The Siberian peashrub is a perennial leafy shrub with an extensive root system. Each plant is self-compatible, meaning that it can self-fertilize and produce seed without another plant nearby. Being self-compatible makes it easy for a planted Siberian peashrub to produce seed that can spread to areas where it was not planted. Siberian peashrub grows in forest understories, edge habitats, and open, grassy habitats.

Origin and Spread

Siberian peashrub is native to Central and East Central Asia. It has been planted in the United States as an ornamental and shelterbelt plant. Siberian peashrub can now be found in most northern and western U.S states. It has been reported in most north and central counties in Minnesota.

Refer to EDDMapS Distribution Maps for current distribution.

Don't be fooled by these look-alikes

  • Honey locust, Gleditsia triacanthos (native) – Honey locust is a tree with leaves that look similar to Siberian peashrub leaves. Honey locust leaves can be once or twice compound and have 18-28 leaflets per leaf on once compound leaves and up to 150 leaflets on twice compound leaves. Siberian peashrub has 8-12 leaflets per leaf. Honey locust flowers are white and Siberian peashrub flowers are yellow.
  • Bristly locust, Robinia hispida (invasive) – Bristly locust has pink flowers and has stems covered in red bristles.
  • Forsythia, Forsythia species (non-native) – Forsythia includes several species of ornamental shrubs. Forsythia have yellow flowers with four petals. Forsythia plants have simple, oval-shaped leaves, not compound leaves with multiple leaflets as Siberian peashrub has.
 
Regulatory Classification

This species is a Minnesota Department of Agriculture Restricted Noxious Weed meaning it is illegal to import, sell, or transport. 

Threat to Minnesota
  • Siberian peashrub invades savanna and woodland edge environments where it competes with native shrubs.
  • It also invades disturbed grasslands and can convert them into shrublands.
  • Siberian peashrub changes soil chemistry by increasing nitrogen levels. This can negatively affect native species that are adapted to low-nutrient environments.
What you should do

One way that invasive plant seeds and fragments can spread is in soil. Sometimes plants are planted purposefully. You can prevent the spread of invasive plants.

PlayCleanGo: Stop Invasive Species in Your Tracks

  • REMOVE plants, animals & mud from boots, gear, pets & vehicle.
  • CLEAN your gear before entering & leaving the recreation site.
  • STAY on designated roads & trails.
  • PLANT non-invasive species.
Native Substitutes
 
Control Methods

Mechanical control can be done with repeated prescribed burning. Siberian peashrub will resprout from the base, but be weakened with repeated burning and may eventually die. Pulling seedlings can also be effective.

Herbicide control can be done using systemic herbicides, which are taken up by plants and move within the plant, killing leaves, stems, and roots. Cut plants will resprout if the stump is not treated with herbicide after cutting. Immediately after cutting (within 2 hours), apply an herbicide containing triclopyr (Garlon 3A/Vastlan, Garlon 4, or other brush killers with triclopyr) or glyphosate (Roundup) to the cut stump to prevent re-sprouting. Always follow label instructions for herbicides. Herbicides can be applied to cut stumps with a paintbrush, wick applicator such as a dauber or "buckthorn blaster," or a low volume sprayer. In cases where more than a few plants are treated, add an indicator dye (available where pesticides are sold), such as Mark-It Blue, to the herbicide to mark which cut stumps you have sprayed.

For basal stem treatment, a method that applies chemical through the bark, low volume spray applications can be made with Garlon 4, Pathfinder II, or similar oil-based products. This application method uses triclopyr ester mixed with an oil diluent (i.e. Bark Oil Blue, kerosene) applied directly to the bark of Siberian peashrub from the root collar up about 12-18 inches. An ultra-low volume spray wand should be used to minimize herbicide use and reduce the potential for non-target injury to nearby plants.

Reporting

Report new occurrences by submitting a report through EDDMapS Midwest, emailing Arrest The Pest, calling Arrest the Pest (1-888-545-6684), or contacting your local county agricultural inspector.

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